Clock



FIG. 1 shows a front perspective view of my design for a clock;

FIG. 2 shows a front elevational view of my design for a clock;

FIG. 3 shows a rear elevational view of my design for a clock;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a left side view thereof; and,

FIG. 7 is a right side view thereof.

The broken lines in the drawings are for illustrative purposes only and do not form part of the claimed design. 

The ornamental design for a clock, substantially as shown and described. 